The role of the male accessory gland fluid in stimulating vitellogenesis in Aedes taeniorhynchus

Injection of 20‐hydroxyecdysone (20‐OH‐ecdysone) at high concentrations (5.0 μg) into intact or decapitated female Aedes taeniorhynchus induced vitellogenin synthesis, whereas low concentrations (5.0 ng) were ineffective. Injections of male accessory gland fluid (MAGF), however, at a concentration that was equivalent to 0.25 of the content of a pair of accessory glands, into intact or decapitated A. taeniorhynchus induced viteliogenin synthesis only in intact females. Ovariectomized mosquitoes did not synthesize vitellogenin after MAGF injection or blood feeding. Females that were first injected with MAGF and decapitated 12 h later synthesized viteliogenin at a rate that was 80% of intact controls. Egg development neurosecretory hormone (EDNH) activity in the heads of ovariectomized or intact females injected with MAGF was 9.0 pmol/min/head and 2.5 pmol/min/head, respectively, indicating that MAGF does not stimulate the corpus cardiacum (CC) to release EDNH. Incubation of MAGF and EDNH with fat bodies failed to induce vitellogenin synthesis. These results indicate that in A. taeniorhynchus the MAGF induces the ovary to release corpus cardiacum stimulating factor, which then signals CC to release stored EDNH.